The present invention relates to a transparent hard coat film, particularly a transparent hard coat film suitable for a surface base material of a transparent touch panel or the like used on the display screen of a color CRT, a flat panel display or the like.
Conventionally, a transparent hard coat film obtained by subjecting a transparent polymer film to a surface roughening treatment is used for a transparent touch panel provided on the display screen of a CRT, flat panel display or the like, so as to prevent viewing difficulty due to glare from external light reflected by the display screen. In the surface roughening treatment perfomed on the transparent polymer film, a transparent hard coat layer containing inorganic particles or synthetic resin particles having a relatively uniform diameter of several xcexcm to a few tens of xcexcm is generally used so as to prevent glare without degrading transparency.
On the other hand, owing to advances in the color performance of CRTs and flat panel displays using touch panel displays and also higher color definition in various displays, a problem has arisen that, when a conventional transparent hard coat film subjected to a surface roughening treatment for preventing glare is used in a touch panel, the high-definition color screen, particularly the white portions thereof, produce glare.
Accordingly, an object of the present invention is to provide a transparent hard coat film having excellent display visibility, wherein color screen glare is not caused even when the film is laminated on a high-definition color display surface, and capable of preventing glare due to external light without causing blurring of the image display due to degradation of transparency, as is experienced with conventional transparent hard coat films.
As a result of extensive studies on the rough surface layer of the conventional transparent hard coat film, the present inventors found that, (1) since inorganic particles or synthetic resin particles having a relatively uniform diameter of several xcexcm to a few tens of xcexcm are used to form the rough surface, the protrusions and recesses, which are regular and smooth, have about the same intervals as the intervals of the RGB light-emitting points, (2) since these regular and smooth protrusions and recesses on the surface act as lenses, the RGB light-emitting points, which are the source of the color display, are enlarged and emphasized, and (3) consequently the light emitting white portions of the screen, where all the RGB light-emitting points emit light, become particularly notable sources of glare. They accomplished the present invention based on this knowledge.
Specifically, the present invention provides a transparent hard coat film characterized in that a transparent hard coat layer composed of at least an ionizing radiation curable resin and two or more kinds of inorganic particles having different average diameters is provided on a transparent polymer film.
The transparent hard coat film of the present invention is also characterized in that the inorganic particles are at least two kinds of inorganic particles having an average diameter of 1-15 xcexcm and an average diameter of 5-50 nm.
In the above-described transparent hard coat film of the present invention, the transparent hard coat layer may consist of a single layer or multiple layers. In the case of one layer, the layer contains two or more kinds of inorganic particles having different average diameters. In the case of multiple layers, each of two or more kinds of inorganic particles having different average diameters may be incorporated in a different layer. In this case, inorganic particles having larger diameter are contained in the layer(s) on the side of the transparent polymer film and inorganic particles having smaller diameter are contained in the outer layer(s).
That is, a transparent hard coat film according to a first aspect of the present invention is characterized in that a single-layer transparent hard coat layer composed of at least an ionizing radiation curable resin and two or more kinds of inorganic particles having different average diameters is provided on a transparent polymer film.
A transparent hard coat film according to a second aspect of the present invention is characterized in that a first transparent hard coat layer containing at least an ionizing radiation curable resin and inorganic particles having an average diameter 1-15 um and a second transparent hard coat layer containing at least an ionizing radiation curable resin and inorganic particles having an average diameter of 5-50 nm are provided successively on a transparent polymer film.
The transparent hard coat film of the present invention is also characterized in that the first transparent hard coat layer has a film thickness of 2-15 xcexcm and the second transparent hard coat layer has a film thickness of 0.2-1.5 xcexcm.